Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF INVENTION
Vertically Stacked Carded Aramid Web
Useful in Fire Fighting
Clothing
FIELD OF THE INVENTION
The present invention is directed to a vertically stacked carded
aramid web which can be employed as an insulating thermal liner in fire
fighting clothing.
BACKGROUND OF THE INVENTION
Most turnout gear commonly used by firefighters in the United
States comprise three layers, each performing a distinct function. There is
an outer shell fabric often made from flame resistant aramid fiber such as
poly(meta-phenylene isophthalamide)(MPD-l) or poly(para-phenylene
terephthalamide)(PPD-T) or blends of those fibers with flame resistant
fibers such as polybenzimidazoles (PBl). Adjacent to the outer shell fabric
is a moisture barrier and common moisture barriers include a laminate of
Crosstech~ PTFE membrane on a woven MPD-I/PPD-T substrate.
Adjacent the moisture barrier is an insulating thermal liner which generally
comprises a batt of heat resistant fiber.
The outer shell serves as initial flame protection while the thermal
liner and moisture barrier protect against heat stress.
U.S. Patent 5,645,296 discloses flexible fire and heat resistant
materials formed from an intimate mixture of organic intumescent filler and
organic fibers.
U.S. Patent 5,150,476 discloses a layered insulating fabric useful
as a lining commonly worn by fire fighters which comprises an
intermediate layer of pleated material wherein the pleats define between
an array of air pockets that function as thermal insulation.
A need is present for an improved insulating material which can be
employed as an inner lining in fire fighting clothing.
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SUMMARY OF THE INVENTION
The present invention is directed to a vertically stacked carded
aramid web and a method of preparation wherein the web has a
lengthwise rectangular cross-section with continuous parallel ridges and
grooves of approximately equal spacing wherein said web comprises 5 to
95 parts by weight carded p-aramid fibers and 95 to 5 parts by weight
carded m-aramid fibers, on a basis of 100 parts by weight of p-aramid and
m-aramid fibers.
(n a preferred embodiment the web comprises:
an area density in a range from 0.5 to 7 ounces per square yard,
a height of in a range from 2 mm to 50 mm and
a peak frequency which occurs in a range from 4 to 15 times per
inch; and
0 to 20 parts by weight of binder.
A preferred use of the vertically stacked structure is as an inner
lining in fire fighting clothing.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram illustrating the process for making new
corrugated structures of the present invention.
Fig. 2A is a schematic view of a machine of the prior art which has
two reciprocating elements which may be used with the process of the
present invention for manufacturing the desired vertically stacked
structures of the present invention.
Fig. 2B is a schematic view of the driving mechanism for the two
reciprocating elements of the machine of the prior art shown in Fig. 2A.
Fig. 3 is a photographic representation of the vertically stacked
structure of the present invention.
Fig. 4A is a perspective view of the vertically stacked structure of
the present invention.
Fig. 4B is a cross-sectional view of an alternative embodiment of
the vertically stacked structure of the present invention.
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Fig. 4C is a cross-sectional view of a further alternative
embodiment of the vertically stacked structure of the present invention,
Fig. 4D is a cross-sectional view of another alternative embodiment
of the vertically stacked structure of the present invention.
Fig. 4E is a cross-sectional view of another alternative embodiment
of the vertically stacked structure of the present invention.
Fig. 4F is a cross-sectional view of another alternative embodiment
of the vertically stacked structure of the present invention.
Fig. 5 is a perspective view of a thermal liner employing the
vertically stacked structure of the present invention.
Fig. 6 is a pictorial representation of a fire fighter's garment
incorporating the vertically stacked structure of the present invention.
Fig. 7 is a sectional side elevation view of a composite fabric of the
fire fighter's garment of Fig. 6.
DETAILED DESCRIPTION OF THE INVENTION
Criticality is present in the present invention is formation of a
uniform vertically stacked carded aramid web by use of two different
carded aramid fibers, namely a p-aramid fiber and a m-aramid fiber.
As employed herein the term aramid means polyamide wherein at
least 85% of the amide (-CONH-) linkages are attached directly to two
aromatic rings. Additives can be used with the aramid and, up to as much
as 10 percent by weight of other polymeric material can be blended with
the aramid or that copolymers can be used having as much as 10 percent
of other diamine substituted for the diamine of the aramid or as much as
10 percent of other diacid chloride substituted for the diacid chloride of the
aramid. In the practice of this invention, the aramids most often used are:
poly(paraphenylene terephthalamide) and poly(metaphenylene
isophthalamide).
Two distinct embodiments of the present invention are present,
namely (1 ) an embodiment which employs a combination of p-aramid and
m-aramid fibers wherein the vertically stacked structure is held in a fixed
position by use of binder material, and (2) an embodiment which employs
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a combination of p-aramid and m-aramid fibers wherein the vertically
stacked structures are held in a fixed position by use of a supporting
material on either one or both sides of the vertical stacking and vertically
stacked structure is attached to the supporting material such as by
~ stitching.
In both embodiments carded aramid fiber will be present in an
amount of 5-95 parts by weight para-aramid and 95-5 parts by weight m-
aramid (on a basis of 100 parts by weight). A preferred amount of aramid
fibers will be 30 to 70 parts by weight p-aramid fibers and 70 to 30 parts by
weight m-aramid fibers.
In the event a binder is present to hold the vertically stacked aramid
in place it will generally be present in an amount of 1 to 20 parts by weight.
Although higher amounts of binder can be present, an added amount is
not considered necessary to impart a degree of rigidity to the vertically
stacked structure. Lower amounts of binder will generally denote less
rigidity. It is understood that the binder can be a fiber or can be employed,
for example, as powder sprinkled on the web or structure or as a liquid
applied to aramid fibers and subsequently solidified. The composition of
the binder is not critical provided the binder imparts a degree of rigidity. A
preferred class of binders are binders which are fixed in place by
application of heat. It is understood that the binder will be selected on the
basis of the final application of the vertically stacked structure.
Illustratively, a lower melting binder is less desirable in a fire fighting
article.
To provide structure consolidation, the feed blends comprise binder
fibers having binder material that bonds at a temperature that is lower (i.e.,
has a softening point lower) than any (i.e., lower than the lowest) softening
point of the said staple fibers in the feed blend, in the amount by weight
about 1 to about 20 parts by weight of blend, the batt being heated in an
oven to activate the binder material.
Sheath/core bicomponent fibers are preferred as binder fibers,
especially bicomponent binder fibers having a core of polyester
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homopolymer and a sheath of copolyester that is a binder material, such
as are commonly available from Unitika Co., Japan (e.g., sold as MELTY).
Useful classes of binders include polypropylene, polyethylene,
5 polyester all of them either by themselves or as a combination in side-by-
side or sheath/core bicomponent fiber configuration.
In the event a binder is not employed in conjunction with the
vertically stacked structure then the vertical stackings are held in place by
use of supporting structures such as a film or cloth on one or both sides of
the vertical stacking. The supporting structures typically are physically
connected to the vertical stackings such as by heat bonding, mechanical
stress (pressure) or by stitching.
The fiype of supporting structures are not critical and will be
selected in conjunction with known end uses of the vertically stacked
structure. Examples of suitable support materials include thermal lining
fabrics such as more fully illustrated below in a description of thermal liner
fabrics.
Referring to Fig. 1, a preferred embodiment of a process for forming
a vertically stacked p-aramid/m-aramid fiber blend structure is illustrated.
The process illustrated in Fig. 1 for making vertically stacked fibrous
structures includes several steps. First, a fiber stock comprising a bale of
p-aramid and a bale of m-aramid fiber material in raw form is presented.
The fiber stock is shown at 10 in Fig. 1. These bales are tightly packed
mass of staple fiber, weighing, for example, approximately 500 pounds
(227 Kg).
Properties of the individual fibers (before being formed into
structures) desirable to manufacture the final vertically stacked structure of
the present invention include denier per filament and crimp frequency.
Denier is defined as the weight in grams of 9000 meters of fiber and is
thus a measure in effect of the thickness of the fiber which makes up the
structure. Crimp of a fiber is exhibited by numerous peaks and valleys in
the fiber. Crimp frequency is measured as the number of crimps per inch
(cpi) or crimps per centimeter (cpcm) after the crimping of a tow. It has
been found, through extensive testing, that fibers having a denier per
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filament of about 0.5 to about 10 (.55 -11 decitex per filament), cut length
of about 0.5 to 4 inches (1.3 cm - 10.2 cm) and crimps per inch of about 6
to about 15 (2.4 to 5.9 crimps per cm ) are particularly useful for the
vertically stacked structure of the present invention.
The fiber can be formed from para-aramids fibers sold under the
trademark KEVLAR~ by E.I. du Pont de Nemours and Company of
Wilmington, Delaware (hereinafter "DuPont") and meta-aramid fibers sold
under the trademark NOMEX~ by DuPont.
Clumps of the fiber stock are removed one after another and then
fed to a picker, which is shown at 12 in Fig. 1. At the picker, the fiber is
opened up. A binder fiber is also sent to the picker as shown at 16 in Fig.
1, and the binder fiber is also opened up at the picker. Binder fibers of
many different materials can be used, however, the preferred binder used
is MELTY 4080 (commercially available from Unitika Co., Japan), which
has a core of polyester homopolymer and a sheath of copolyester. Binder
fibers are especially useful for improving the stability, dimensional and
handling characteristics of the structure of the present invention, once it is
formed. For example, if the blend of fibers and binder fibers is heated, ,
during the heating step, the binder fibers melt and bond the fibers such
that the vertically stacked structure of the present invention retains its
desired configuration, i.e., specific height, peak frequency and area
density, as will be discussed below. The structure may be stabilized
without the use of a binder fiber but with a mechanical technique such as
needle punching or thermal point bonding. Any modifier, such as a flame-
retardant material, may also be added in addition to the binder fibers to
obtain desired functional characteristics. It is also within the scope of the
present invention to use a pre-blended fiber stock which already includes
binder fibers, thereby eliminating the need for mixing the binder fibers in
the picker.
The process of the invention further comprises feeding the opened
up fiber mixture/blend and the opened up binder fiber to a blender, such
as air-conveyed blender 14 as shown in Fig. 1, to form a uniform mixture.
The process of the present invention further comprises carding the blend
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to form a fibrous web. This carding is performed by a card as shown at 18
in Fig. 1 in order to form a fibrous web. The fibrous web is then sent, via a
conveyer (not shown), into an Engineered Structure with Precision (ESP)
machine 22 and an oven 23, the combination being shown generally at 20
in Fig. 1. The structure may be compressed or calendered 21 to achieve
the desired height/thickness. Machine 22 is known in the art, as disclosed
in WO 99/61693, and is shown in Figs. 2A and 2B herein.
As shown in Fig. 2A, machine 22 includes two synchronously
reciprocating elements 24 and 26 connected to a driving mechanism 28. A
tie rod 30 connects element 24 to a sliding fitting 32 and also connects
sliding element 32 to a flexible knuckle joint 34. Sliding fitting 32 keeps
tie
rod 30 in its vertical position. A bolt 38 connects tie rod 36 to an arm 40,
which in turn is connected to a shaft 42. It is shaft 42 which imparts a
vertical reciprocating motion to reciprocating element 24. A pair of tie rods
44 connect shaft 42 to driving mechanism 28 via a bolt 46 and a tie rod 48.
Tie rod 48 is connected to driving mechanism 28 by a bolt, and a tie rod
54 is connected to driving mechanism 28 by a bolt 52. A bolt 56 connects
tie rod 54 to a pair of tie rods 58, which connect to a shaft 60. Shaft 60
imparts horizontal reciprocating motion to reciprocating element 26. Shaft
60 connects to an arm 62, which is connected via flexible knuckle joints 64
and 66 and a tie rod 68 to a sliding fitting 70. The sliding fitting keeps the
tie rod in its horizontal position.
As shown in Fig. 2B, driving mechanism 28 includes a driving shaft
72 with two cam rolls 74 and 76. Driving mechanism 28 reciprocates
element 24 vertically and element 26 horizontally. The cam rolls allow
synchronized phase movement of the reciprocating elements. Element 24
is reciprocated perpendicular to the lengthwise direction of the fibrous
web, and element 26 is reciprocated parallel to the lengthwise direction of
the fibrous web. These reciprocating motions thereby vertically fold the
web to form a closely packed, vertically stacked structure and
simultaneously move it forward (i.e., horizontally in the process direction
away from the fibrous web).
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After the structure is shaped into its desired form, it is passed
immediately into an oven, such as oven 23 as shown in Fig. 1, where it is
heated to bond and consolidate it so that it maintains its vertical stackings.
As the structure exits the oven, it is in the form of a folded structure. The
resulting vertically stacked structure of the present invention is shown at
100 in Figs. 3 and 4A. The bonded and consolidated structure may be
compressed if desired to achieve the desired height/thickness.
Various configurations of the vertically stacked structure of the
present invention are shown in Figs. 4A - 4F, As can be seen in these
Figs., the vertically stacked structure of the present invention has an
essentially lengthwise rectangular cross section. The vertically stacked
structure as shown in Fig. 4A has an upper surface 102 and a lower
surface 104, a side wall 106 and a side wall 108, and end walls 110 and
112. As can be seen from Figs. 4A - 4F, the vertically stacked structure
comprises a plurality of continuous alternating peaks and valleys of
approximately equal spacing. The peaks and valleys are shown at 114,
114', 114" and 114"', 114"" and 114""', and at 116, 116', 116", 116"',
116"" and 116""', respectively in Figs. 4A - 4F. In addition, the vertically
stacked structure comprises a plurality of parallel aligned pleats, or
vertical
stackings, 118, 118', 118" and 118"', 118"" and 118""' which are arranged
in accordion-like fashion and which extend in alternately different
directions between each peak and each valley. The parallel aligned pleats
may be interconnected by protruding fibers of the adjacent pleats. The
upper surface of the structure is formed by the peaks, while the lower
surface is formed by the valleys. The side walls 106, 108 are formed by
the ends of the pleats, and the end walls 110 and 112 are formed by the
last pleats of the structure. In the embodiments of Figs. 4A - 4C, E and F,
the peaks and the valleys are generally rounded. The pleats of the
vertically stacked structure can be saw-tooth, as shown in the embodiment
of Fig. 4B, triangular shape, as shown in the embodiment of Fig. 4C,
square/rectangular shape, as shown in the embodiment of Fig. 4D, "C"
shaped as shown in the embodiment of Fig. 4E or "<" shaped as shown in
the embodiment of Fig. 4F. Moreover, the vertical stacking may be
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vertical as shown in Figs. 4A, 4C, 4D, 4E and 4F or inclined as shown in
Fig. 4B.
Important features of the vertically stacked structure of the present
invention, which have been predetermined by extensive testing, are area
density, height and peak frequency. Specifically, the vertically stacked
structure of the present invention has an area density of 0.5 to 7 oz/yd2
preferably 2 to 4 oz/yd2, a height of 2 mm to 50 mm, preferably 3 to 8 mm,
and a peak frequency which occurs at 4 to 15 times per inch (1.58 - 5.91
times per cm) preferably 8 to 12 times per inch. The area density of the
vertically stacked structure is controlled by fixing the throughput rate of
the
web and the output rate of the structure. The height of the vertically
stacked structure is controlled by the thickness of a push bar (not shown)
used for forcing the web away from reciprocating member 26 as shown in
Fig. 2A and into the oven. Peak frequency is measured as the total
number of peaks per inch (peaks per centimeter) of structure. For a given
thickness of web, controlling the peak frequency is obtained by adjusting
the speed of the reciprocating elements (i.e., the number of times per
minute the reciprocating elements make contact with the fibrous web to
form a crease (stratify)) and the speed of the conveyor belt which is used
for moving the vertically stacked structure away from reciprocating
member 24 in Fig. 2A. Further adjustment in structure height may be
made by compressing the structure after it has been formed.
The protective fabric used as the heat insulating material,
particularly as a thermal liner 11 (Figure 5) in garments such as fire
fighter's turnout suit, includes a face cloth of woven material 130 that has
flame- and fire-resistant properties and an inner layer of spunlaced
nonwoven material 120 that is thin and light and is thermally insulative.
The face cloth is closest to the body while inner layer is away from the
body. Sandwiched between the inner and face layers of material is an
intermediate layer of material that is formed into a vertically stacked
sfiructure 100 comprising a plurality of continuous alternating peaks and
valleys as previously discussed. The intermediate layer of vertically
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stacked structure holds the face and inner layers of the composite thermal
liner apart.
While preferred materials have been suggested for the thermal finer
5 fabric, it should be understood that the many layers that make up the
thermal liner 11 including fabrics chosen from a wide range of
possibilities, Material choices might, for example, be made from the group
consisting of meta-aramid, other aramids, polynosic rayon, flame-resistant
polynosic rayon, viscose rayon, flame-resistant viscose rayon, other flame-
10 resistant cellulosics such as cotton or acetate, cotton, flame-resistant
polyester, polybenzimidazole, polyvinyl alcohol, polytetrafluoroethylene,
wool, flame-resistant wool, polyvinyl chloride, polyetheretherketone,
polyetherimide, polyethersulfone, polychlal, polymide, polyamide,
polyimide-amide, polyolefin, carbon, modacrylic, acrylic, melamine, and
glass and blends made therefrom. Additional materials for use as face
cloth 130 and the inner layer 120 include spun-laced knits, nonwovens,
wovens, stifich-bonded fabrics and weft-insertion fabrics. Other suitable
materials might also be selected consistent with the spirit and scope of the
present invention depending upon the particular intended use of the fabric.
The face 130, intermediate 100, and inner 120 layers of material
are securely bound together by lines of stitching 16 of a thermally resistant
thread, The stitching extends through all three layers of the fabric and that
preferably is configured in a quilted pattern defining contiguous regions 17
of the fabric 11. The tension applied to the stitching as it is sewn through
the layers of material preferably is sufficient to collapse the pleated
intermediate layer between the outer and inner layers along the lines of
stitching as illustrated at 18. However, the stitching can be loose to avoid
collapse of the intermediate layer and thus maintain maximum spacing
between the inner and outer layers, if desired.
The stitching 16 functions to maintain the vertically stacked
structure intermediate layer 100 securely in position between the face
cloth 130 and inner layer 120 and thus preserves its deformed
configurations by preventing the material of the intermediate layer from
stretching out or bunching together as a garment is worn and washed.
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The quilted stitching pattern thus preserves the integrity of the pleats
formed in the intermediate layer material so that the spacing between the
face and inner layers and the air pockets defined therebetween are
maintained throughout normal use and cleaning conditions. In this way,
the fabric retains its performance qualities even after long use of a
garment.
As mentioned briefly above, the material from which the inner and
intermediate layers 120 and 100 are formed can be the same if desired
with insulation qualities of its own. In this way, a wearer of a garment such
as the turnout jacket of Fig 5 having the fabric of this invention as a liner
positioned adjacent the body of the wearer is insulated from heat and
flame by the fabric.
A fire fighter's garment 34 incorporating the fabric of this invention
is not only light and highly protective, it also tends to keep the fire
fighter
comforfiable with a stretchable vertically stacked structure intermediate
layer 100 while fighting a fire.
Figure 6 illustrates a fire fighter's protective garment that
incorporates the vertically stacked structure of this invention as an interior
thermal liner or barrier. The illustrated garment is comprised of a
protective coat 34 having a trunk portion 36, sleeves 37, and collar 38.
The outer shell 150 of the coat 34 can be formed of a number of flame and
abrasion-resistant materials such as woven aramid or polybenzimidazole
fabrics commonly used in the construction of such garments. The
moisture barrier material 160 is next in from the outer shell 150 and the
thermal inner liner 11 is next. These layers of fabric are bound together at
the edges of the garment.
Figure 7 is an enlarged sectional side elevation view of the
composite fabric used in fire fighter's turnout suit 34 of Fig. 6 showing the
special configuration and interrelationships of the various layers of the
fabric. The turnout suit typically comprises an outer shell fabric 150 that is
heat- and abrasive-resistant, a moisture barrier 160 as the next layer and
a thermal liner 11.
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The vertically stacked structure of the present invention can also be
used to make other articles, such as sleeping bags, cushion seats,
insulated garments, filter media, insulating curtains, flame blockers, wall
coverings, etc. These articles have the desired characteristics obtained by
determining the desired area density, height and peak frequency of
vertically stacked structure used. For any article made with the vertically
stacked structure of the present invention, either a single layer or plural
layers of structure may be used, depending on the desired properties of
the final article.
To further illustrate the present invention, the following examples
are provided. All parts and percentages are by weight unless otherwise
indicated.
Example 1
Clumps of the fiber stock, consisting of three components, are
removed one after another and then fed to a picker. The three
components are (i) Kevlar~ Type 970 (2.25 dpf, 1.5 inch cut length, ) (ii)
Nomex~ Type 40 (1.5 dpf, 1.5 inch cut length), and (iii) Unitika binder fiber
MELTY 4080 Type S74 (4.0 dpf, 1 inch cut length). The relative
concentration by weight is 45% Kevlar~ p-aramid, 45% Nomex~ m-
aramid and 10% binder fiber. The opened-up fiber mixture was well
blended in an air-conveyed blender to form a uniform mixture. The well
blended fiber mixture was carded to form a fibrous web. Carding machine
operating at input speed of 1.5 feet per minute while the card dofFer was
operating at a speed of 49.2 feet per minute. The well blended, uniform
card web was then converted into the vertically stacked structure
comprising a plurality of continuous alternating peaks and valleys of the
present invention. The accordion-like arrangement of the structure which
extends in alternately different directions between each peak and each
valley was formed by the driving mechanism reciprocating element,
moving up and down vertically at a frequency of 300 revolutions per
minute. The vertically folded structure immediately entered into an oven at
a speed of 3.7 feet per minute. The oven was maintained at 400°F to
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bond and consolidate the structure to maintain its vertical stacking. The
structure height was 10 mm, with an area density of 102 g/m2 and a peak
frequency of 10 peaks/inch. The structure height was subsequently
reduced to 5 mm by applying pressure and heat.
The thermal protective performance (TPP) test used for quantifying
a fireman's turnout garment was measured on a composite sample
consisting of three major components - outer shell, moisture barrier and
thermal liner. The outer shell used was a 7.0-8.0 oz/yd2 (nominal 7.5)
woven fabric made of Kevlar~ fiber (60%) and PBI fiber (40%). The
moisture barrier fabric was 4.0-5.0 oz/yd2 (nominal 4.5) Crosstech~ fabric,
a'PTFE laminated to fabric of Nomex~ brand fiber. The thermal liner
consisted of the vertically stacked structure sandwiched (inserted)
between a layer of 1.5 oz/yd~, NomexO liner E-89, spunlaced fabric and a
2.0-2.5 (nominal 2.2) inner face fabric of woven Nomex~-fiber as the
inside of the garment. The total composite weight of the assembly was
18.8 oaJyd2. The composite assembly was tested for TPP with the outer
shell exposed to the heat source per procedure described in NFPA-1971.
The TPP obtained was 46.3 Ca!/cm2.
The control consisted of an identical outer shell, a moisture barrier
and the woven Nomex~ inner facing fabric. The commonly used
commercial thermal insulation consisted of three layers of Nomex~ E-89
brand spunlaced fabric. Assembled with these components, this therri~al
insulation resulted in a TPP of 42.0 at a measured assembly weight of
20.3 o~/yd2.
Example 2
Vertically folded structures were made substantially the same as in
Example 1 except wifih varying height, peak frequency and area density,
shown in Tabie 1. They were sandwiched between the spunlaced fabric
and face cloth and then added to a outer shell and moisture barrier to form
a composite. The only variable was the vertically folded structure
properties of the thermal liner assembly.
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Example 3
Thermal liner inserts sandwiched between the spunlaced fabric and
the face cloth were made consisting of a carded web which had been
cross-lapped. This was obtained by blending a 45% Nomex~ fiber, 45%
Kevlar~ fiber and 10% binder fiber Type MELTY S74 in a Rando blender.
The well blended fibers were sent to a master chute-fed card. The web
from the card was cross-lapped and sent to an oven. The oven was
maintained at preheat 424°C and heat zone 330°F. The thruput
rate was
12 feet/minute. A composite structure was formed essentially as
described in Example 1 with a weight of 19.3 oz/yd2. The resulting TPP
was 45.0 Cal/cm2.
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Com
osite
ThicknessArea Peak FreqCompressedWeight TPP Thickness
Item (mm) Den (peaks Thickness*(oz/yd2)(cal/cm2)(mil)
(glm2) er in mm
2-1 10 68 6.1 18 42.9 517
2-2 10 102 8.6 18.6 44.5 S36
2-3 10 136 10.9 19.2 48.4 S82
2-4 10 170 13.8 20.5 57.9 66S
2-S 10 204 16.7 21.6 62.1 6S8
2-6 10 237 21.1 22.5 70.1 692
2-7 IS 102 8.6 I8.8 46.6 635
2-8 20 102 8.6 19.2 48.2 80S
2-1 9.7 17.35 40.57 323
2-2 7.11 18.32 43.89 267
2-3 8.33 19.2 47.32 337
2-4 7.56 19.84 51.19 300
2-S 7.16 20.45 53.3 261
2-6 S.S8 21.58 58.74 263
2-7 3.96 18.64 46.89 183
2-8 7.62 18.87 48.2 231
Kevlar~ Type 970, 2.25 dpf,1.5 inch cut - 45%
NomexO Type 450, 1.5 dpf, 1.5 inch cut - 45%
Unitika Binder Type S74, 4.0 dpf, 1.0 inch cut-10%
Den means density
Freq means frequency
